Hundreds of people wandered around the town centre looking for the "invisible" artworks.

The launch night was the culmination of two years of work as part of an ambitious public art commissioning project.

In Burnley, a group of 15 teenagers undertook an art journey in which they learned about art and how public art can benefit a town.

They chose acclaimed UK art collective Greyworld to create an installation for the town and the result is entitled Invisible.

The works are in 19 sites across the town centre and are only visible when subjected to ultraviolet light. The pictures include old movie posters, a shop front, a vending machine and a goldfish bowl as well as images of "local heroes", people who were nominated as having made a lasting contribution to the town.

The main celebrations were at the bandstand in St James's Street where there was a performance by the Big Bollywood Brass Band and visitors who completed an arts trail were given Big Art goodie bags.

Afterwards, there was a reception at Koko's where speeches were given by invited guests including Burnley Borough Council leader Coun. Gordon Birtwistle and Mr Chris May from Creative Partnerships.

Burnley is one of seven sites across the UK to be involved in the Big Art Project and was the first to unveil its artwork. The whole process is being filmed for a series which is due to be aired on Channel 4 later this year.

• Click here to view a slideshow of the launch

• Click here more information and a downloaded map showing where to locate the works